1. Field of the Invention
The present invention relates to hinge assemblies and, particularly, to an automatically opening hinge assembly for foldable devices such as mobile phone, personal digital assistant (PDA) and so on.
2. Discussion of the Related Art
At present, perhaps the most popular portable electronic device in the marketplace is the foldable cellular telephone, which generally includes a cover section and a body section. The cover section and the body section are rotatably interconnected with a hinge, for switching the telephone between an open position and a closed position.
One kind of hinge assembly is described in China Publication Number 200410052435.7 published on Jun. 7, 2006. Referring to FIGS. 20 and 21, the hinge assembly 60 includes a shaft 61, two pins 62, a compression spring 63 and a housing 64. The shaft 61 has a fixing portion 612 formed at one end thereof. The housing 64 is a hollow cylinder with an open end. The housing 64 has an engaging portion 642 formed at one end thereof opposite to the open end. The housing 64 defines two spaced sliding slots 644 along a peripheral wall thereof. Each sliding slot 644 has a convex point 6442. In assembly, the compression spring 63 and the shaft 61 are received in the housing 64. One end of each pin 62 is fixed in the shaft 61, the other end of each pin 62 is received in a corresponding sliding slot 644. The pins 62 may slide along the sliding slots 644. The engaging portion 642 of the housing 64 is engaged with one of a cover and a body of a portable electronic device, and the fixing portion 612 of the shaft 61 is engaged with the other of a cover and a body of a portable electronic device.
When the cover is close relative to the body, the pins 62 are positioned at one end of the sliding slots 644 under the compression spring 63. When the cover needs to be opened relative to the body, the cover is opened by hand so as to bring the shaft 61 to rotate. Accordingly, the shaft 61 causes the pins 62 to slide along the sliding slots 644 until the pins 62 pass over the convex point 6442. Then, the cover is stopped to apply force, and the pins 62 automatically bring the shaft 61 to rotate about the housing 64 under the force of the compression spring 63, thus allowing the cover to rotate about the main body. However, a user must open the mobile phone using both hands to a predetermined degree so as to further automatically open the cover. This makes the mobile phone inconvenient to use in situations where the user has only one hand free.
Therefore, a new hinge mechanism is desired in order to overcome the above-described problems.